Diesters of 2-methyl-2-neopentyl-1, 3-propanediol



United States Patent 3,254,114 DTESTERS 0F Z-METHYL-Z-NEDPENTYL- LS-ROPANEDIOL Paul F. Strohm, Philadelphia, Edward G. Shay, King of Prussia, and Charles A. Signorino, Bridgeport, Pa, assignors to The Atlantic Refining Company, Philadeiphia, Pa, a corporation of Pennsylvania No Drawing. Filed July 3, 1962, Ser. No. 207,397 4 Claims. (Cl. 26(2-476) This invention relates to synthetic ester lubricants and their preparation and is particularly concerned with diesters of substituted propanediols having unusual thermal stability.

With the development of jet and rocket propelled aircraft there has developed an increasing need for lubricants requiring special properties which are not possessed by conventional mineral lubricating oils. In general, mineral lubricating oils undergo marked viscosity changes With changes in temperatures and have relatively high pour points when they have a usable viscosity at high temperatures. Furthermore, hydrocarbon oils suifer oxidation or other thermal decomposition at high temperatures. When hydrocarbon lubricating oils having a low pour point are used they usually contain a considerable amount of volatile material which is lost at high temperatures and thus readily effects the lubricating power of the oil.

Thus, lubricants for use in turbojet and turboprop type aircraft must possess a high viscosity index in order to promote adequate lubrication over a wide range of temperatures. They must also have a high oxidation and thermal stability in order that they may retain their useful properties after operation for a long period of time at high temperatures. They must have a low pour point in order that they may function at a low temperature and high flash point to avoid risk of fire at high temperature operation and loss of lubricant by evaporation.

Complex ester-type synthetic lubricants prepared by combinations of glycols, dibasic acids, monobasic acids, and alcohols are well-known in the synthetic lubricant art,

The diesters principally investigated up to the present time have been aliphatic materials. While the aliphatic diesters heretofore known have been generally satisfactory for use as synthetic lubricants, they have been, in general, lacking in one important propertyg namely, that of thermal stability.

It is, therefore, an object of this invention to provide a new class of synthetic ester lubricants which are not subject to many of the disadvantages inherent in hydrocarbon lubricating oils.

It is another object of this invention to provide synthetic lubricating oils which were not known heretofore.

It is another object of this invention to provide synthetic lubricating oils which have a high oxidative stability, a low volatility and exceptional thermal stability.

It is another object of this invention to provide an improved class of synthetic ester lubricants particularly adapted for use in applications for which conventional hydrocarbon lubricants are unsuitable.

It is another object of this invention to provide a new class of synthetic ester lubricants prepared from substituted propane diols.

It is another object of this invention to provide heretofore unknown diesters of Z-methyl-Z neopentyl-1,3- propanediols which have particular utility as synthetic lubricants.

Other objects will become apparent from the description and claims that follow.

These and other objects are attained by means of this invention as described in detail hereinafter with particular reference to certain preferred embodiments there- Patented May 31, 1%66 of. The compounds embodying this invention are synthetic lubricants comprising diesters having the general formula OII wherein A and A are aromatic substituted acyl radicals selected from the group consisting of radicals and wherein R is selected from the group consisting of hydrogen and an alkyl radical which may be normal or branched in structure and contains up to about 8 carbon atoms. The alkyl radical attached to the aromatic nucleus is preferably selected from the group consisting of methyl and ethyl radicals and is preferably substituted in the para position.

The diesters embodying this invention are prepared by reacting 1 molar proportion of Z-methyl-Z-neopentyl-1,3- propanediol with 2 molar proportions of an aralkyl monocarboxylic acid preferably selected from the group consisting of phenyl acetic acid, alpha-phenyl propionic acid, beta-phenyl propionic acid, and the mono-alkyl phenyl substituted acetic and propionic acids. The esters thus obtained are characterized by having exceptionally high thermal stability.

The synthetic diester lubricants of this invention may be used alone, particularly in applications where it is undesirable to employ additives which would leave a residue or which might decompose or be volatile at elevated temperatures. In some cases it may be desirable to employ the propanediol esters described herein in conjunction with other additives such as anti-oxidants, anticorrosion agents, pour point depressors, viscosity improvers, or extreme pressure additives. The synthetic lubricants described in this invention may also be used in the preparation of greases as Well as in admixture with a hydrocarbon lubricating oil, other synthetic ester lubricants, mineral oil, or any of the well-known conventional lubricating materials.

The synthetic ester lubricants of this invention are prepared, as stated above, by heating 2 molar equivalents of the desired aralkyl moncarboxylic acid defined herein with 1 molar equivalent of the substituted propanediol.

The conditions under which the esterification is effected may be varied in accordance with well-known practice for eifecting esterification of a diol with an acid. In most cases, it is desirable to heat the mixture of acid and propanediol to a temperature ranging between about C. to about C. for a time sufficient to cause evolution of 2 molar equivalents of water. If desired, this water may be removed as formed but this aspect is not necessary in preparing the synthetic lubricants of this invention. The water may be removed by azeotroping it with a solvent such as benzene, toluene, or Xylene or the water may be distilled off without the use of such a solvent. When the esterification is substantially complete the diesters obtained are washed with an alkaline material to remove any unreacted acid and the esters 'are further purified by distillation at a reduced pressure.

The following examples are intended only as illustrative of the instant invention and are not to be construed as limitative.

EXAMPLE I Alpha-diisobutylene was oxidized with air in the pres-.

ence of a cobalt catalyst at a temperature of 230 F. under a pressure of 120 p.s.i.g. There was formed 1,2- epoxy-2,4,4-trimethyl pentane which was isomerized by passage over alumina at a temperature between 530 F. and 570 F. There was produced 2,4,4-trimethyl pentanal which was subsequently reacted with formaldehyde in the presence of sodium hydroxide at a temperature between 140 F. and 150 F. to produce 2-methyl-2-neopentyl-l,3-propanediol, which was purified by recrystallization from toluene.

EXAMPLE II Into 500 ccs. of xylene containing 2 grams of paratoluene sulfonic acid there was placed 160 grams of 2- methyl-2-neopentyl-1,3 -propanediol prepared in accordance with the method set forth in Example I and 310 grams of beta-phenyl propionic acid. The mixture was refluxed and the water of reaction was removed continuously by an azeotropic distillation with xylene through a Dean-Stark receiver. The reaction mixture was washed with water to remove acidic impurities. The xylene solvent was removed by distillation and the product was vacuum distilled. That portion of the product boiling between 210 C.- and 230 C. at 0.4 mm. of mercury pressure was collected and further purified by redistilling under a pressure of 0.25 mm. of mercury. The portion of product boiling between 206 C. and 209 C. was collected. This material had a refractive index at 25 C. of 1.5160 and was identified by infrared analysis.

EXAMPLE III EXAMPLE IV 2-methyl-2-neopentyl-1,3 -prop anediol bis alpha-phenyl propionate) was prepared by reacting 32 grams of 2- rnethyl-2-neopentyl-1,3-propanediol with 52 grams of 'alpha-phenyl propionic acid in accordance with theprocedure set forth in Example II. The product had a boiling range at 0.2 mm. of mercury pressure of 185 C. to

194 C. and a refractive index of 1.5120. This material was also identified by infrared analysis.

EXAMPLE V 2-methyl 2 neopentyl 1,3 propanediol bis(gammaphenyl butyrate) was prepared by reacting 40 grams of 2-methyl-2-neopentyl-l,3-propanediol with 75 grams of alpha-phenyl butyric acid in accordance with the procedure set forth in Example II. The product had a boiling range of 0.3 mm. of mercury pressure of 187 C. to 195 C. and a refractive index of 1.5125. This material was also identified by infrared analysis.

EXAMPLE VI tive index of 1.5203. This material was also identified by infrared analysis.

EXAMPLE VII 7 2-butyl-2-ethyl-1,3-propanediol bis(beta-phenyl propionate) was prepared by reacting grams of 2-butyl-2- ethyl-1,3-propanediol with grams of beta-phenyl propionic acid in accordance with the procedure set forth 'in Example II. The product had a boiling range at 0.8

mm. of mercury pressure of 225 C. to 235 C. and a refractive index of 1.5150. This material was also identified by infrared analysis.

EXAMPLE VIII The thermal decomposition temperatures of the diesters prepared in Examples II to VII, inclusive, are shown in Table I. These values were determined in an Isoteniscope apparatus as described by E. S. Blake et al., J. Chem. Eng. Data, Volume 6, p. 87 (1961). The thermal decomposition measurements were obtained by plotting vapor pressure versus temperature as log p vs l/T where p is the pressure in mm. of mercury and T is the Table I Thermal No. Diester Decomposi- On Point, F.

1 From Example II .1 650 2 From Example III 613 3 From Example IV 620 4 From Example V 527 9 1,1,1-trimethylol propane triheptanoat 584 7 bis(2-ethyl hexyl) sebacate 555 5 From Example VI 584 6 Fom Example VII 587 8 2-methyl-2-neopentyl-1,B-propanediol dipe- 568 largonate.

From the data shown in Table I it is apparent that the thermal stabilities of the diesters of 2-methyl-2-neopentyl- 1,3-propanedio1 of this invention are far superior to the thermal stability of other diester materials which have been used as synthetic lubricants. The diesters of this invention are superior to other diesters of substituted 1,3- propanediols. (Compare 1, 2 and 3 with 5 and 6.) The diesters of this invention are superior to aliphatic diesters of 2-methyl-2 neopentyl-1,3-propar1ediol (compare 1, 2 and 3 with 8). The diesters of this invention are superior to lubricants used in commercial jet engines (compare 1, 2 and 3 with 7). The diesters of this invention are superior to synthetic lubricants presently being considered for military aircraft (compare 1, 2 and 3 with 9). The diesters of this invention are superior to diesters prepared from 2-methyl-2-neopentyl-1,3-propanediol and other aralkyl monocarboxylic acids (compare 1, 2 and 3 with 4).

We claim: 1. A diester having the general formula AOCHzCCIIzO-A wherein A and A are aromatic substituted acyl radicals 2. 2 methyl 2-neopentyl-1,3-propanedio1 bis(pheny1 selected from the group consisting of acetate).

3. 2 methyl 2-neopentyl-1,3-propanedio1 bis(alpha- I phenyl propionate).

5 4. 2 methyl Z-neopentyl-1,3-pr0panediol :bis(betaphenyl propionate). I

References Cited by the Examiner an UNITED STATES PATENTS l TCH2 10 $048,608 8/1962 Girard et a1. 260-475 LORRAINE A, WEINBERGER, Primary Examiner.

H. G. MOORE, Examiner.

15 R. E. MASSA, Assistant Examiner. radicals. 

1. A DIESTER HAVING THE GENERAL FORMULA 